1. Field of the Invention
There have been numerous reports of monoclonal antibodies directed to tumor associated antigens. However, only a few of these have been found useful to detect tumor associated antigens in sera. For the most part, where an antigen has been found to be associated with neoplastic tissue, but not with adjacent normal tissue, it has subsequently been found that the antigen is present in normal tissue at other sites. Therefore, in many instances the degree of false positives destroys any value to the detection of the antigen as a diagnostic.
At the present state of the art, it is not necessary that the detection of the antigen in a physiological fluid be a perfect predictor of cancer. In many situations, where a tumor is removed, one can monitor a change in the presence in a physiological fluid of a specific epitopic marker as diagnostic of the effective removal of the tumor or the continued presence of the tumor. In other situations, two or more markers may be employed, providing for an enhanced certainty of the neoplastic condition. In other situations, such as imaging, it need only be that the marker is sufficiently more prevalent on the surface of the neoplastic cell as compared to the normal cell, so that the tumor may be distinguished.
It is therefore of great value to be able to define specific epitopes associated with tumors, which allow for diagnosis of neoplasia in physiological fluids, e.g. blood or serum, with a reasonable degree of accuracy, where the marker is used by itself or in conjunction with other markers.
2. Description of the Prior Art
Koprowski et al., Lancet (1982) i:1332-1333, reports the monoclonal antibody designated 19-9, related to diagnosing Lewis blood type as indicative of gastrointestinal cancer. The antibody reacts with approximately 60% of the sera from colon cancer patients. Magnani et al., Cancer Res. (1983) 43:5489-92, reported that the antigen to which 19-9 binds is a sialylated Lewis.sup.a structure or epitope that is present on mucins released into the sera of cancer patients. Bast et al., N. Engl. J. Med. (1983) 309:883-887, reports a monoclonal antibody that reacts with an antigen, designated CA125, which is a high molecular weight glycoprotein and is found in 82% of the sera of patients with ovarian carcinoma. Rauvala, J. Biol. Chem. (1976) 251:7517-7520, reports the sialylated derivative of lacto-N-fucopentaose III as a novel ganglioside of human kidney, which is called sialylated Le.sup.x.
The significance of sialylation in neoplasma has been the subject of many reports. See, for example, Warren et al., Proc. Natl. Acad. Sci. USA (1972) 69:1838-1842; Van Beek et al., Br. J. Cancer (1977) 36:157-165; Warren et al., Biochem. Biophys. Acta (1978) 516:97-127; Glick, Biochemistry (1979) 18:2525-2532; and Yogeeswaran and Tao, Biochem. Biophys. Res. Commun. (1980) 95:1452-1460. Many monoclonal antibodies raised against cancer cells have been reported as having their main activity against terminal carbohydrate structures such as sialylated Lewis.sup.a (Magnani et al., J. Biol. Chem. (1982) 257:14365-14369); Lewis.sup.b (Brockhaus et al., ibid (1981) 256:13223-13225); and Lewis.sup.x (Hakomori et al., Biochem. Biophys. Res. Commun. (1981) 100:1578-1586).